Signals such as hormones, light, and gravity control diverse physiological processes in plants. Thimann, K. V., Hormone Action in the Whole Life of Plants (Univ. Mass. Press, Amherst) (1977); Leopold, A. C et al., Plant Growth and Development (McGraw-Hill, New York) (1975). Although the biochemical and molecular events involved in the transduction of these signals are not clearly understood, calcium is known to act as a messenger in signal transduction. Helper, P. K. et al., Annu. Rev. Plant Physiol. 36:397-439 (1985); Poovaiah, B. W. et al., CRC Crit. Rev. Plant Sci. 6, 47-103 (1987); Poovaiah, B. W. et al., Physiol. Plant. 69:569-573 (1987); Roux, S. J. et al., CRC Crit. Rev. Plant Sci. 5:205-236 (1987). As in animals, many of the effects of calcium ions in plant cells are mediated by a calcium-binding regulatory protein, calmodulin. Roberts, D. M. et al., CRC Crit. Rev. Plant Sci. 4:311-339 (1986). Calmodulin is a highly conserved, heat-stable, acidic protein with four calcium-binding domains. Poovaiah, B. W. et al., CRC Crit. Rev. Plant Sci. 6:47-103 (1987); Roberts, D. M. et al., CRC Crit. Rev. Plant Sci. 4:311-339 (1986). Calmodulin binds to calcium, undergoing a conformational change, and then interacts with enzyme-molecules. The Ca.sup.2+ -calmodulin complex can regulate enzyme activities directly and indirectly through protein phosphorylation by activating protein kinases. Poovaiah, B. W. et al., CRC Crit. Rev. Plant Sci. 6:47-103 (1987); Roberts, D. M. et al., CRC Crit. Rev. Plant Sci. 4:311-339 (1986); Veluthambi, K. et al., Science 223:167-169 (1984); Ranjeva, R. et al., Annu. Rev. Plant Physiol. 38:73-93 (1987). In plants, enzymes such as NAD kinase, Ca.sup.2+ -ATPase, H.sup.+ -ATPase, quinate:NAD.sup.+ oxidoreductase and protein kinases have been shown to be regulated by calcium and calmodulin. Poovaiah, B. W. et al., CRC Crit. Rev. Plant Sci. 6:47-103 (1987); Roberts, D. M. et al., CRC Crit. Rev. Plant Sci. 4:311-339 ( 1986).
The structure of the calmodulin gene and its expression have been well studied in animals. Means, A. R. et al., Calcium and Cell Physiology, ed. Marme, D. (Springer, New York) 127-139 (1985); Mujaal, R. P et al., Proc. Natl. Acad. Sci. USA 78:2330-2334 (1981 ); Lagace, L. et al., J. Biol. Chem. 258:1684-1688 (1983); Putkey, J. A. et al., J. Biol. Chem. 258:11864-11 870 (1983). In animal cells, intracellular levels of calmodulin have been shown to be unaffected by a number of steroid and peptide hormones. Means, A. R. et al., Physiol. Rev. 62:1-38 (1982). However, calmodulin levels were found to be elevated in transformed cells and also at the G.sub.1 /S boundary of the growth cycle of mammalian cells. Chafouleas, J. G. et al., Cell 28:41-50 (1982); Chafouleas, J. G. et al., Cell 36:73-81 (1984); Chafouleas, J. G. et al., Proc. Natl. Acad. Sci. USA 78:996-1000 (1981 ); Zendegui, J. G. et al., Mol. Cell. Biol. 4:883-889 (1984). In these cases, the changes in calmodulin were found to be accompanied or preceded by changes in the level of its mRNA. Chafouleas, J. G. et al., Cell 36:73-81 (1984); Zendegui, J. G. et al., Mol. Cell. Biol. 4:883-889 (1984).
Calmodulin protein has also been studied in plants. In particular, a calmodulin protein in plants has been isolated and characterized. Poovaiah, B. W. et al., CRC Crit. Rev. Plant Sci. 6:47-103 (1987); Roberts, D. M. et al., CRC Crit. Rev. Plant Sci. 4:311-339 (1986). To further understand calmodulin gene expression in plants, a plant calmodulin cDNA clone (pPCM-1) has been isolated and sequenced. Jena, P. K. et al., PNAS (USA) 86:3644-3648 (1989). By using the cDNA clone, it has been shown that signals such as auxin and light regulate the expression of calmodulin. Jena, P. K. et al., PNAS (USA) 86:3644-3648 (1989). To further study the role of plant calmodulin, particularly the consequences of altered levels of intracellular calmodulin, several independent transgenic tobacco plants expressing either sense or antisense calmodulin mRNA driven by the cauliflower mosaic virus (CaMV) 35S promoter have been generated. Wang, A. et al., Plant Physiol. Suppl. 93:914 (1990). There were no abnormalities in growth or development in these sense and antisense transgenic plants.
In potato plants, the role of calcium and calmodulin in the tuberization process has been studied. Balamani, V. et al., Plant Physiol. 80:856-858 (1986); Balamani, V. et al., Plant Physiol. 80:856-858 (1986); Jena, P. K. et al., PNAS (USA) 86:3644-3648 (1989). In particular, it has been shown that increased intracellular calcium levels increases tuberization. Balamani, V. et al., Plant Physiol. 80:856-858 (1986). Potatoes are a major food crop in the United States and therefore, controlling tuberization by genetically altering potato plants would be very desirable.
It would thus be desirable to control growth and development of plants. It would also be desirable to control growth and development of plants by controlling the expression of a gene encoding calmodulin. It would also be desirable to control growth and development of potato plants by controlling the expression of a gene encoding calmodulin. It would further be desirable to control growth and development of plants without employing chemicals foreign to the plant. It would also be desirable to acquire long-term control of growth and development of plants by genetically altering the plants,